By contrast, mammals have brains that “are designed for learning — they are designed to change — in sync with their environments.” We humans have evolved to adapt to cold weather, to fashion new tools, to adventure to new lands.

So why is change so hard for us, when we are, apparently, so used to it?

Even as we are creatures who learn, we are also creatures of habit. The American philosopher and psychologist William James described it aptly in the 19th century:

“Any sequence of mental action which has been frequently repeated tends to perpetuate itself, so that we find ourselves automatically prompted to think, feel, or do what we have been before accustomed to think, feel, or do, under like circumstances.”

Understanding how we form habits and why it’s so difficult to break them can be the key to making a change just a little bit easier — because while habits are incredibly helpful to our daily lives, they also make us resist doing things in new ways.

It’s hard to break away from the status quo

Learning a new environment, or a new way of being, is generally more taxing than sticking to the status quo. Michael Shermer, the founding publisher of Skeptic magazine and a columnist for Scientific American, told me that “it’s a heavier cognitive load to learn something new, to explore new environments” because it requires the brain to make new neural connections.

Learning engages an area of the brain Lewis has written is “the seat of appraisal, judgment, and consciousness” — the prefrontal cortex. Only after a great deal of practice does a new skill become a habit, at which point it demands less analysis and attention. Lewis explains that “it becomes something you automatically spin off from your striatum” — a relatively primitive part of the brain — “with very little prefrontal involvement.”

The characteristics of habit — that it is both hard won and hard to change — help us understand why, for example, it’s difficult to start driving a stick shift after years of driving cars with automatic transmission. And these same characteristics also help explain why we get stuck in more complex situations that we know are not good for us. “One of the best examples of that are abusive or codependent relationships,” Lewis said. “Why can’t we walk away from them? Because they’re deeply habitual. The synaptic patterns have been deeply carved, shall we say, by a lot of emotion and repetition.”

Individual temperaments and habits of thought

How we approach change can also vary based on a host of other factors that may be reinforced by habits of thinking, such as our past experiences, our tendency toward anxiety or depression, our general approach to novelty and risk-taking (what scares one person can thrill someone else), and our tendency toward what therapists call “rigid” thinking about how the world “should” work.

Kimberly Williams, a clinical psychologist who works with children on the autism spectrum, gifted children, and children with learning disabilities, told me some people appear to be wired to struggle with change. “Some people are just quite flexible and fluid in their thinking. A lot of the patients I get are rigid thinkers,” she says. “In order for them to change” — it could be as simple as transitioning from a video game to the bath — “they need a lot of cajoling and preparation and behavior management.”

On the other side of things are people who are drawn by temperament to novelty and the thrill of the new.

“I think there is a subset of intensely dopamine-dominant people for whom actually change is good because it’s tied into their dopamine reward system,” said Amy Banks, a psychiatrist and director of advanced training at the Jean Baker Miller Training Institute at Wellesley College. These people might once have been our earliest explorers, helping humanity by discovering new lands while risking disease, starvation, and conflict in the process. In the modern context, such people experience excitement, rather than fear, upon landing in a foreign place, surrounded by strangers. Banks described the thrill of the new as offering a hit of euphoria for such adventure-seekers.

The power of context in our willingness to change

Banks, who wrote a book called “Wired to Connect,” told me that, depending on one’s temperament and past experiences, (among other factors), change can trigger a fight-or-flight response and throw our higher-order thinking processes for a loop — and for good reasons, evolutionarily speaking. “Our fear centers are attached to things like surprise and novelty, and in a primitive world, all of those things are associated with potential danger, literally,” she told me. “If it’s a new situation, we’re counting on that cognitive [process] to help us think through why we’re going to be OK. But if we’ve not been there before, we don’t have that.” Even the anxiety that comes with change can itself become a habit.

Of course, the context of change matters a great deal. Even if it’s ultimately for the good, it matters whether it’s a change we’ve chosen, or one that’s been foisted upon us. And it matters whether we’re taking a risk in an arena we consider ourselves to be strong in. Past experiences and how we process them can eventually turn into habits — perhaps because we avoid things that scare us, taking a catastrophic view when things don’t turn out as we hoped, or perhaps because we embrace the new, and come to think of ourselves as resilient. Someone who ended a bad relationship and landed on her feet, helped along by the support of family and friends, may hesitate less about cutting her losses the next time.

“People are actually very complex” in how they approach change, says psychologist Harriet Lerner. “I would resist change in a car, or learning something technological, but I am very adventuresome in my work as a psychologist and I’m very adventuresome and brave about opening up difficult conversations with the people who are close to me,” she said.

Another complexity of change is how it impacts our social lives, and whether we have the help of those we love when we’re initiating that divorce, move, adoption, or whatever it is. I’ll tackle that theme in my next post — the last in this series about the science of change.

Libby Copeland is a journalist in New York who has written for Slate, The New Republic, The Washington Post, New York magazine, Smithsonian Magazine, The Wall Street Journal, Fast Company, Glamour and more. Previously she was a staff reporter and editor for The Washington Post for over a decade.